The present invention generally relates to a keyboard, such as a computer keyboard, and in particular to a pushbutton structure of a keyboard which generates a pulse-like reaction when it is depressed for indicating the depression thereof.
A computer keyboard includes a plurality of pushbuttons each comprising a cap accessible and depressible by a user. A conventional design of the pushbutton comprises a post, which may be hollow, extending from the cap. The post is partially received and is axially movable within a guiding bore. To ensure proper movement of the cap, the post must have a size large enough to reduce the risk of being jammed in the guiding bore. This, however, is contrary to the current trend of miniaturization in the electronic and computer industries.
Pushbuttons having caps supported by a pair of links pivotally connected to each other in a cross form are also known. This structure effectively reduces the space required by a pushbutton. A rubber member is positioned under the cap. The depression of the cap collapses the rubber member. The resiliency of the rubber member restores the cap back to its original un-depressed position. Such a restoration force provided by the rubber member, however, is generally not sufficient to effectively return the cap back to the un-depressed position.
Furthermore, the rubber member only offers a very limited reaction during the depression of the pushbutton. This may sometimes be ignored by the user when the user is depressing the pushbutton and thus making no clear indication of the depression of the pushbutton to the user.
It is thus desirable to provide a pushbutton structure which overcomes the above problems.
Accordingly, an object of the present invention is to provide a pushbutton structure which generates a pulse-like reaction during depression of the pushbutton for providing a clear indication of the depression of the pushbutton.
Another object of the present invention is to provide a pushbutton structure having a strong restoring force for returning the pushbutton from a depressed position to a released position.
To achieve the above objects, in accordance with the present invention, there is provided a pushbutton structure of a keyboard comprising a cap supported on a base board by a linkage consisting of first and second links pivoted together whereby the cap is movable from a released to a depressed positions when depressed. Each link has upper and lower pivots respectively connected to the cap and the base board. The links have two side bars connected between the upper and lower pivots thereof. A cross bar is connected between the side bars of the first link. A resilient arm extends from the cross bar and forms a nub on a free end thereof. A rigid arm extends from one side bar of the second link and has a wedge section having first and second surfaces forming an apex therebetween. The nub of the resilient arm is in contact engagement with the first surface when the cap is at the released position. The nub slides over the apex to reach and engage the second surface when the cap is depressed and moved to the depressed position whereby a pulse-like reaction is generated. Two spring arms extend from the base board with free ends thereof receivingly engaging recesses defined in corresponding side bars for biasing the cap toward the released position. The spring arms deform when the cap is depressed whereby the spring arms help returning the cap back to the released position when the depression is released.